Turbine or compressor rotor



June 6, 1950 w, BODGER I 2,510,734

TURBINE 0R COMPRESSOR ROTOR Filed April s, 1946 2 Sheets-Sheet 1 FIG. 2

FIG. 3

F|G.l' I

I0 I I INVENTOR WALTER KENNETH BODGER ATTORNEY June 6, 1950- w. K. BODGER 2,510,734

' TURBINE 0R COMPRESSOR ROTOR FIG.4

INVENTOR WALTER KENNETH BODGER ATTORNEY Patented June 6, 1950 TURBINE OR COMPRESSOR ROTOR Walter Kenneth Dodger, Glastonbury, Com, al-

signor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application April 6, 1946, Serial No. 860,134

This invention relates to turbine rotor It is well known that in axial-flow turbine and compressor blades, as in propeller blades, the centrifugal loads on the blade apply a pitchreducing moment tending to move the blade into a low-pitch position. In certain types of blades, however, especially in gas turbines, the blade is given a twist between its ends for the purpose of improving the turbine operation. When the rotor is spinning, the twisted blade tends to untwist under centrifugal loads in a direction normally to increase the pitch of the blade. In many cases, this untwisting moment is enough greater than the pitch-reducing moment to twist the blade. A feature of this invention is an arrangement for preventing either moment from twisting the outer end of the blade. The inner end of the blade is prevented from twisting by its connection with the hub.

Another feature is a lock on the blade shroud by which to prevent the blade from untwisting during operation.

In some rotors each blade has an integral shroud which abuts the shrouds on the adjacent blades. These shrouds may be rectangular in shape or, for minimizing stresses in the shrouds, may be rhombic or diamond-shaped. The diamond-shape of the shroud prevents twisting of the blades in one direction during rotation but does not prevent twisting in the opposite direction. A feature of the invention is a step on each of the shrouds interlocking with a corresponding step on the adjoining shroud to prevent twisting of the blade. Since the contour of the diamond-shaped shroud is such that the blade untwisting moment is not opposed, the interlocking steps become especially important for preventing the untwisting of the blade.

Damping of vibra tions in turbine blades is obtained in many cases by the interengagement between adjoining surfaces of the shrouds. A feature of the invention is an arrangement of the step on the shroud for the purpose of increasing the damping action.

Other objects and advantages will be apparent from the specification and claims, and from the accompanying drawings which illustrate an embodiment of the invention.

Fig. 1 is an elevation of the several turbine blades.

Fig-2 is a plan view of the shrouds looking radially inward. mz'ig. 3 is a view substantially on line 33 of 4 Claims. {01. 253-77) As shown in Fig. 1, the disk 2 of the rotor carries a number of blades 4, each of which has an integral shroud element 6 at its outer end. As shown more clearly in Fig. 4, the blade 4 has a substantial twist between the root 8 and the shroud. The leading edge iii of the blade is tipped forward with respect to the direction of rotation of the rotor and the trailing edge i2 is tipped rearward.

with reference to Fig. 2, each shroud 6 is substantially diamond-shaped in plan view, the shroud having this contour to minimize the amount of overhang of the shroud from the blade which supports it, and at the point where it meets the shroud the blade extends between the acute angle corners of the diamond-shape.

The pitch-reducing moment normally tends to twist the blade in a clockwise direction as viewed in Figs. 2 and 3, but twisting in this direction is resisted by the shape of the shrouds since as will be apparent, clockwise turning of the shrouds merely brings the adjoining surfaces of the rhombic-shaped shrouds into closer contact.

The blade untwisting moment however, which as above stated is in many cases much greater in magnitude than the pitch-reducing moment, tends to twist the outer end of the blade in a counter-clockwise direction. To resist this untwisting moment, each shroud has steps I which engage with steps on the adjoining shrouds and by interlocking prevent counter-clockwise twisting of the shrouds and thereby also prevent the blade from untwisting.

In addition to preventing the untwisting of the blades, which if not resisted might produce a measurable change in the blades, the steps are arranged at such an angle to the adjoining surfaces of the shrouds that when the steps are in interengagement the friction between the adjoining shroud surfaces will provide a substantial amount of frictional damping of blade vibrations. The angle shown is substantially a right angle.

It is thus apparent that the interlocking steps on the shroud prevent untwisting of the blade and also assure a frictional damping of blade vibrations by interengagement between the adjoining shrouds during rotation.

It is to be understood that the invention is not limited to the specific embodiment herein illustrated and described, but may be used in other ways without departure from its spirit as defined by the following claims.

I claim:

Fig. 4 is an elevation on a larger scale of a 1. A rotor having a number of substantially turbine blade.

radially extending blades, a substantially dia- 8 mend-shaped elementontheouterendof eachofthe eswith-theaenteangled corners oftbeshroud acenttotheleadingandtrailingedgesof blades.theshrouds on adjacent blades having their end surfaces substantially in amusement. each blade being twisted between its innerandouterendaandinterengagingstepson the adjoining end surfaces of said shrouds to prevent untwisting of the blades, said steps having their inter-engaging surfaces arranged at a substantialangletotheplanecftheshroudto resist untwisting of the blades.

zarotorhavinganumberofsubstantially radiallyextendingblades,eachofwhichhasa twist between its inner and outer ends, a substantially diamond-shaped shroud element on the outer end of each blade with the acuteanglcd corners of the shroud located adjacent to the leading and trailing edges of the blade, the shrouds on adjacent blades having their adjoining end surfaces extending at an oblique angle to the side surfaces of the shrouds, and in engagement thereby to prevent twisting of the blades in one direction, and interlocking steps on the adjoining end surfaces of the shrouds to prevent twisting of the shrouds and blades in the opposite direction, the interensas ns surfaces ofsaidsteps extendingatasubstantialangleto the plane of the shroud.

3. A rotor having a hub, a number of substantlally radially extending blades projecting from the periphery of the hub. each blade having a twist between its inner and outer ends, a substantially diamond-shaped shroud element on the outer end of each blade with the acuteangled corners of the shroud located adjacent totheleading andtrailimedgesofthebladathe auam side surfaces of the shrouds being substantially in parallel planes, the end surfaces of the shrouds extendingatobliqueanglestotheparallel planes of the side surfaces of the shrouds and in contact with each other, each end surface having a step therein between its ends with the surfaces at opposite sides 'of the step substantially parallel to each other.

4. A rotor having a hub, a number of substantially radially extending blades projecting from the periphery of the hub, each blade having a twist between its inner and outer ends, a substantially diamond-shaped shroud element on the outer end of each blade with the acute-angled corners of the shroud located adjacent to the leading and trailing edges of the blades, the side surfaces of the shrouds being substantially in parallel planes, the end surfaces of the shrouds extending at oblique angles to the parallel planes of the side surfaces of the shrouds in contact with each other, each end surface having a step therein between its ends with the sin'faces at opposite sides of thestep substantially parallel to each other, the surface of said step being substantially at right angles to the remainder of the end surface of the shroud.

WALTER KENNETH BODGER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,247,400 Herr Nov. 20, 1917 2,378,372 Whittle June 12, 1945 2,398,140 Beppner Apr. 9.1946 

